package com.yunxi.poc.starbucks.util;

import java.math.BigDecimal;
import java.math.RoundingMode;

/**
 * 经纬度距离工具类
 *
 * @author shiyuan.xlc
 * @since 2021-08-09
 */
public class DistanceUtil {
    private static final double EARTH_RADIUS = 6378.137;

    private static double rad(double d) {
        return d * Math.PI / 180.0;
    }

    /**
     * 通过经纬度获取距离(单位：千米)
     *
     * @param lat1
     * @param lng1
     * @param lat2
     * @param lng2
     * @return
     */
    public static double getDistance(double lng1, double lat1, double lng2, double lat2) {
        double radLat1 = rad(lat1);
        double radLat2 = rad(lat2);
        double a = radLat1 - radLat2;
        double b = rad(lng1) - rad(lng2);
        double s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a / 2), 2)
                + Math.cos(radLat1) * Math.cos(radLat2)
                * Math.pow(Math.sin(b / 2), 2)));
        s = s * EARTH_RADIUS;
        s = Math.round(s * 10000d) / 10000d;
        BigDecimal bd = new BigDecimal(s);
        return bd.setScale(4, RoundingMode.HALF_UP).doubleValue();
    }

    public static void main(String[] args) {
        // https://lbsyun.baidu.com/jsdemo.htm#a6_1
        // 108.960339,34.336834
        // 108.965266,34.336719
        double distance = DistanceUtil.getDistance(
                121.504132, 31.242452,
                121.506554, 31.24118);
        System.out.println(distance);
    }
}
